Japanese unexamined patent application publication No. JP-A-2002-244055 (Hereinafter, Patent Document 1) describes a related art image forming apparatus. The related art image forming apparatus generates an image by subjecting photosensitive elements to scan exposure through use of a laser beam originating from a semiconductor laser, or the like. It has been proposed that the related art image forming apparatus of this type be equipped with a beam detect (BD) sensor. When the laser beam reaches a home position, the laser is forcibly illuminated. The BD sensor detects the continuous illumination of the laser beam at the scan home position for scan exposure and generates a BD signal. The laser beam is then modulated in accordance with image data on the basis of a detection timing of the BD signal. It has also been proposed that the related art image forming apparatus of this type enable adjustment of a timing at which the semiconductor laser is forcibly illuminated in order for the BD sensor to detect the laser beam. The adjustment of the timing can be made, for example, according to a characteristic of a scanner motor for deflecting the laser beam.
Although not described in Patent Document 1, it has also been proposed to commence continuous illumination at a predetermined period corresponding to the predetermined scan speed before the detection of the BD signal, to control an electric current applied to the semiconductor laser for a period before the BD signal is detected, and to adjust an amount of the laser beam.